This invention is in the field of indicators for determining the level of contents in a bulk storage container and in particular such an indicator that is portable and allows the operator to determine the level of contents while standing at ground level outside of the container.
It is often required to find the vertical level of contents in a container. The contents may-be granular or particulate material such as grain or fertilizer in a bin, or a liquid such as fuel in a tank.
There are presently numerous indicators for indicating the level of contents in a container. They range from a simple liquid sight glass on a tank to complex and highly accurate acoustic systems such as are found in U.S. Pat. No. 4,790,183 to Pfost et al. and in U.S. Pat. No. 4,403,508 to Langlois.
The problem with these prior art indicators is that there generally must be a sensor of some sort mounted in each container. Time, expense and planning is required in order to achieve the result. An easily portable and inexpensive indicator that would indicate the level of contents, liquid or granular, in the majority of containers with reasonable accuracy would be beneficial in many situations. All that is often required is an estimate of the contents. For example a farmer could easily find out if a bin was half full or three quarters full and thereby estimate the contents. Where the same indicator could work as well to determine the level in a liquid fertilizer or fuel tank, convenience and economy would be enhanced.
The invention is based on the well known phenomena that the level of contents in a single wall container may be determined by tapping on the wall. Above the contents boundary there is a hollow sound, while below the boundary there is different solid sound. The phenomena is present where the contents are granular or liquid, and where the wall material is metal, wood or any similar sheet material. The difference in sounds is discernable to the human ear with little difficulty.
It is the object of the present invention to provide a portable container level indicator that is simple and economical, and that provides an indication of the level of the contents of a container from the ground level outside the container.
It is a further object of the present invention to provide such an indicator which generates a sound by tapping on the wall of the container. The sound will generally be audible to the operator standing on the ground, but may include electronic pick-up means to transmit the sound to the operator. The tapping mechanism may be electrical, such as a solenoid propelled tapper, or mechanical, such as a spring propelled tapper.